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is a surge protected extension/powerstrip any use without upfront SPDs

psychicwarrior

hello goodly morrow

If a T3 SPD, 'must not' be used, as per 7671,  without upfront (T1+)T2 SPD  (for want of better words) ,  what real value is a plugged in surge protected extension lead/powerstrip  (which is a T3 in effect one presumes) without a T2 somewhere upfront ?

Or is it really just a sacrificial item and really is better to have.

Perhaps the components are pretty useless and cheap in most of the consumer grade surge leads/strips.  May be connected devices (via power blocks and transformers etc) can cope just as well  ;-)

Engineering references and regs are not going to use the anything is better than nothing finger in the air style and have to present a considered, tested and  co-ordinated approach. The consumer market takes a different view it seems and makes little to no effort (does it) to advise that surge protected powerstrips/leads 'must not be used' without upfront SPD,  but if course such is not part of fixed wiring any way so no need, or is there a need . 

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  • 0

    I've been out a few moments ago and bought one from the local 'shed'  :-)  ... just to see  (well it will get used).

    And...  it states on the label on the body that it is a T3 SPD; Uc 255V Uoc 4kV Up 2.5kV.

    So it is a T3   -  with no T2 upfront (in this case) ... but, as noted,  it is not covered by BS7671 of course.

    It is there to sacrifice   :-)

  • 0 in reply to psychicwarrior

    well it rather depends on how many events of each level of severity you expect to get per year, The prolific but low level stuff from domestic sources like spikes from tumble dryer motors reversing will be trapped very well by something like this, as will some external things from the neighbours but not very big surges, but there probably are not that many of those anyway, after all there are plenty of installations with no surge protection at all, and not a lot seems to happen.
    The problem is one of probability, and that is very location dependent.  

    Mike

  • 0 in reply to mapj1

    Yes agreed. A few of us here were having that same discussion ... it being  about location, risk assessment etc  and whether to bother with surge powerstrips/leads.     I've had nothing for decades and have and have had computers, routers and so on like most and nothing has  happened ( that I know of). One never knows though . ;-)

    Perhaps folk with really expensive and/or sensitive equipment might employ them but also as part of a coordinated approach.

    The point in mind  was that although powerstrips etc are not part of fixed wiring (covered by 7671), they (or some) are indeed T3 SPD (point of use).    It seemed that 7671 was suggesting dont fit anything at all unless i is all co-ordinated, or if not that exactly then at least 'must not' fit a T3 unless suitable SPD provisions upfront.  That's why I was delving into the merits of T3  powerstrips.  It must be better than nothing in some cases ... and may be this is the thing.

    Sorry for my wording -  it is poor.

  • 0 in reply to psychicwarrior

    So it is a T3 

    Although live every standard, the specification sets only a minimum requirement - the manufacturer is free to improve on that if they wish (and may well feel inclined to do so if there was a financial incentive to do so). Make something that has the protective characteristics of a T3 but the survivability characteristics of a T2 (or near to) the standards might only allow you to label it a T3 (rather than say T2+T3) but it could still give satisfactory service without an upstream T2.

    BS 7671 of course has to take the precautionary apporach - many thing labelled T3 wouldn't survive without an upstream T2 so that's what it requires. The plug-in filter manufacturers however are playing in a different ball park

       - Andy. 

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  • 0 in reply to psychicwarrior

    So it is a T3 

    Although live every standard, the specification sets only a minimum requirement - the manufacturer is free to improve on that if they wish (and may well feel inclined to do so if there was a financial incentive to do so). Make something that has the protective characteristics of a T3 but the survivability characteristics of a T2 (or near to) the standards might only allow you to label it a T3 (rather than say T2+T3) but it could still give satisfactory service without an upstream T2.

    BS 7671 of course has to take the precautionary apporach - many thing labelled T3 wouldn't survive without an upstream T2 so that's what it requires. The plug-in filter manufacturers however are playing in a different ball park

       - Andy. 

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  • 0 in reply to AJJewsbury

    The best SPD protection would be offered by cascading a T! SPD into a T2 SPD and then very close to the appliance a T3 SPD.  Sounds simple in a UK domestic dwelling until people understand that a type 1 SPD is mainly used for lighting protect/transients so I suspect it would be very rare to find in the average UK 3 bed semi detached house.  A few years ago I started a thread on this forum about should SPD type 2 be mandatory of UK CU/DB and it was met with mixed response.  Caveat time, should a SPD type 2 be mandatory, in my mind yes BUT and this is the caveat.  Is it a new install or an existing one from yesteryear which may not accomodate an SPD type 2.  This is the same type of conundrum of EICR......Does it need to meet the new regulations or the one it was designed an installed to from several years of decades ago?

    To draw a parallel with the EICR / Should SPD be mandatory conundrum

    Look at fire safety systems.  Sometimes those regulations say that system needs to meet the new regulation and that is final.  Any remedial work needs to meet the new regulation for the WHOLE system.  I am sure there are others on this forum that can explain this better than myself.  

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